A collimator is an importation component of a CT system. The collimator is positioned between an X-ray source and the scanned object (e.g. a patient) to control the scanning (e.g., a scanning region, a slice thickness). To improve imaging quality, image data collected in the CT system may be modified before image reconstruction. The modification of the image data may be associated with characteristics of the collimator, such as a collimation width. Thus, it may be desirable to develop systems and methods that modify image data based on the collimation width of the collimator.